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Delta Is Surging. Here's What You Need To Know To Stay Safe

People enjoy an outdoor art exhibition in downtown Los Angeles in early July. Los Angeles County public health authorities are now urging unvaccinated and vaccinated people alike to wear face coverings in public indoor spaces because of the growing threat posed by the more contagious delta variant.
Robyn Beck
AFP via Getty Images
People enjoy an outdoor art exhibition in downtown Los Angeles in early July. Los Angeles County public health authorities are now urging unvaccinated and vaccinated people alike to wear face coverings in public indoor spaces because of the growing threat posed by the more contagious delta variant.

After declining steeply for six months, coronavirus cases are once again on the rise, thanks to the delta variant. The Centers for Disease Control and Prevention reported Friday that new cases are up by nearly 70% in just a week. Hospitalizations are up by nearly 36%.

Surges are most pronounced in areas where vaccination rates are low, but there are also increases in places such as Los Angeles and New York City. And health officials are once again urgently pressing unvaccinated Americans to get the shot.

"This is becoming a pandemic of the unvaccinated," said CDC Director Dr. Rochelle Walensky at a briefing Friday. "If you remain unvaccinated, you are at risk."

But if you're already vaccinated, how worried should you be? Are new precautions called for? Here's what to know about the fast-spreading variant and how to stay safe and protect others.

How much more contagious is the delta variant, really?

Very. As NPR has reported, delta appears to be about 225% more transmissible than the original SARS-CoV-2 strains. One recent preprint study from China found that people who are infected with delta have — on average — about 1,000 times more copies of the virus in their respiratory tracts than those infected with the original strain, and are infectious earlier in the course of their illness.

No matter how you look at it, delta seems to spread faster, explains Helen Chu, associate professor of medicine at the University of Washington.

"You can look at it through modeling, you can look at it through population-level data, and you can look at it simply by putting the virus into the cell and looking at how quickly it infects the next cell," she says. "In all of those measures, it has looked like it's more transmissible."

If I'm vaccinated, can I get sick with delta?

Yes, but don't panic. The vaccines are effective against the delta variant, and though it's still possible to get infected, the vaccines dramatically reduce the risk of serious illness that leads to hospitalization or death. A study from the U.K. found that the Pfizer vaccine is 96% effective against hospitalization from the delta variant after two doses.

A medical assistant administers a COVID-19 test to a person at Sameday Testing on July 14, 2021 in Los Angeles, California. COVID-19 cases are on the rise in most states as the highly transmissible delta variant has become the dominant strain in the U.S.
Mario Tama / Getty Images
Getty Images
A medical assistant administers a COVID-19 test to a person at Sameday Testing this week in Los Angeles.

For context, the CDC has documented a total of 5,492 cases of fully vaccinated people who were hospitalized or died from COVID-19, among the 160 million people have been fully vaccinated in this country.

It's not clear how many of these breakthrough infections are from delta variant cases, but it has quickly become the dominant variant in circulation.

Though the CDC only tracks breakthrough infections that lead to hospitalization and death, some states are keeping track of every case, even the mild ones. In Massachusetts, there have been about 4,450 confirmed breakthrough cases or about .1% of all vaccinated people, as WBUR reported.

What about long COVID-19?

While the risk of getting sick if you're vaccinated is very low, if you do get a symptomatic case, it's likely still possible to end up with long-haul COVID-19 symptoms, according to virologist Angela Rasmussen who works with the Vaccine and Infectious Disease Organization at the University of Saskatchewan in Canada. She notes the data is still quite limited though.

"Even if you don't end up in the hospital, there's certainly a possibility that you could end up with long COVID," she says. "So, the safest thing to do is to avoid being infected altogether."

Should I go back to wearing a mask in public?

Many health experts say that may be a smart move, especially when you're going to be indoors with people who may be unvaccinated and unmasked.

"I would," says Chu of the University of Washington. "I haven't stopped masking indoors."

For her, the calculus has to do with having unvaccinated children at home and not wanting to put them at risk. "Everyone makes their own risk assessment," she says. But with delta cases increasing, "it would be prudent to start doing indoor masking again," she says, particularly as we head into fall.

Masking may especially make sense in places with rising rates of infection, says Bill Miller, a physician and epidemiologist at The Ohio State University.

It's clear that unvaccinated people are not following the recommended indoor-masking guidelines, he notes. "You go into a grocery store and 95% of the people are unmasked when we haven't come close to that level of vaccination," Miller says. This can put people at risk, including children, and people who are immunocompromised.

Miller says he continues to wear a mask in public places, even though he's fully vaccinated. "I know that I am extremely unlikely to get seriously ill. But I also know that if I am exposed, I may become infected and pass it on to others," he says.

Los Angeles County just announced it will reimplement an indoor mask mandate — including for people who are fully vaccinated — because of an increase in cases and concern over the delta variant.

It has been nearly two months since the CDC announced new guidelines declaring that fully vaccinated people don't need to wear masks in most settings, but the World Health Organization still encourages people to mask up.

And health researcher Ali Mokdad of the University of Washington's Institute for Health Metrics and Evaluation says he would like the CDC to reinstate a mask mandate nationwide, given the rise in cases.

"This is the right and scientific thing to do," he says. "That's the only way we can send a signal to the public in the United States that we're not out of danger and we can encourage people to go and get the vaccine."

Do I need a booster shot?

At this point, no. So far the federal government doesn't recommend booster shots to enhance immunity, though it is actively studying the question.

"The CDC and the FDA are working very hard to get as much data as they possibly can to adequately address that question," Dr. Anthony Fauci told NPR's Here & Now this week. Federal health officials and vaccine makers continue to follow participants enrolled in the initial clinical trials to see how well immunity holds up with current vaccinations.

So far, experts say it's encouraging. "The level of antibodies seem to be holding up pretty well, so we have to watch and see what happens over the course of the coming months," Francis Collins, NIH director, told NPR in an interview.

Eventually, as immunity wanes, a booster could be recommended for certain groups, including elderly people. There's also research underway to test a mix-and-match approach to booster shots. Researchers are giving study participants who were originally vaccinated with any of the three authorized vaccines, a booster shot of the Moderna vaccine.

White House COVID-19 response coordinator Jeff Zients said Friday that the administration is ready for the possibility of boosters "if and when the science shows they are needed."

Tourists crowd in to the Midway Geyser Basin July 14, 2021 at Yellowstone National Park, Wy. Yellowstone is one of many national parks seeing record numbers of visitors this summer, while coronavirus cases are rising in many states.
Natalie Behring / Getty Images
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Tourists crowd in to the Midway Geyser Basin on July 14, at Yellowstone National Park in Wyoming. Yellowstone is one of many national parks seeing record numbers of visitors this summer, even as coronavirus cases are rising in many states.

Does delta cause different COVID-19 symptoms?

Maybe. Some doctors and public health departments have reported that people infected with delta have different symptoms from the original, classic signs of COVID-19: cough, loss of taste or smell, and fever. Now, some of the more common symptoms appear to be runny nose, sore throat and headache, according to the ZOE COVID Study, an ongoing app-based research project based in the U.K.

But Chu warns that it's hard to know what's behind that apparent change, "because the population that it's infecting is not the same population that was infected in the prior waves," says Chu. The people getting sick now tend to be much younger, she says.

Since COVID-19 might present differently in younger people, any changes in symptoms could have less to do with the new variant and more to do with the people who are contracting it. "I don't know that you can disentangle that," Chu says.

"This is already a disease that produces a pretty broad range of different clinical presentations in people," adds Rasmussen. She'd like to see better data before concluding the symptoms are, in fact, different.

Do I need those bleach wipes again?

No extra surface cleaning necessary. Even though it's more transmissible, delta still transmits the same way the original SARS-CoV-2 virus does. "This type of virus, which is an RNA virus that is enveloped, tends to transmit [through] respiratory transmission," Chu says.

That's backed up by "some extremely detailed contact tracing" done in the recent preprint from China, says Rasmussen. The researchers "determined that these cases were transmitted primarily through what they called indirect contact, which is most likely inhalation of infectious aerosols [while] breathing shared air, or through direct physical contact," she says.

That means the primary way the virus spreads remains being indoors with someone who is infected and breathing in their droplets or aerosols. With delta, the difference is that the infected person will make many more copies of the virus, faster, which makes it easier to spread.

But in a way, "that's good news," Rasmussen says. "It means that the mitigation measures that we have put in place previously will still work against the delta variant — it's not being transmitted by some other route."

Should I turn down invitations to weddings and other large gatherings?

Many public health experts say it's safe to attend if you're vaccinated, but keep the variant in mind, especially if you're somewhere with rising cases.

OSU's Bill Miller says he encourages mask wearing for an indoor wedding or event "because you're bringing people together from different social networks, creating a great opportunity for an outbreak."

There's a case study that serves as a reminder that the risk is not zero: Six vaccinated people got COVID-19 after attending a wedding near Houston, held in a large, outdoor tent. All of the infected people got symptoms, one was hospitalized, and another person — who had received India's Covaxin vaccine — died, according to a pre-print case study.

As scary as that sounds, "there could be rare events like these where people are in an enclosed tent and very close to each other. But the vast majority, the vast, vast majority of viral transmission is happening indoors," says Chu.

What about kids? Can kids get infected and spread delta?

Yes. Although children tend to have more mild cases of coronavirus, they are certainly susceptible to infection. Children remain the least protected age group, since the vaccine is not authorized for children under the age of 12.

It's possible that children who get infected with the delta variant might have more symptoms than they would if they were infected with an earlier version of the virus. With a more transmissible variant, "when someone gets sick, they tend to have more virus, and they tend to have more symptoms," Chu explains.

That being said, Chu says, typically "children are not that symptomatic from COVID." Her best guess? She thinks delta "probably will not lead to significant numbers of children getting hospitalized."

But there's still a reason to keep your kids masked up in public, and that's the risk they could spread it to more vulnerable people, says Rasmussen. "Even if it doesn't impact them, it could impact other vulnerable people in their household, such as people who may not have had a robust response to the vaccine, people who are immunocompromised."

Copyright 2021 NPR. To see more, visit

Corrected: July 17, 2021 at 12:00 AM EDT
A previous version of this story incorrectly said that in Massachusetts, about .01% of all vaccinated people have had confirmed breakthrough COVID-19 cases. The number is .1%.
Corrected: July 17, 2021 at 12:00 AM EDT
A previous version of this story incorrectly said that in Massachusetts, about 0.01% of all vaccinated people have had confirmed breakthrough COVID-19 cases. The figure is 0.1%.
Allison Aubrey is a correspondent for NPR News, where her stories can be heard on Morning Edition and All Things Considered. She's also a contributor to the PBS NewsHour and is one of the hosts of NPR's Life Kit.
Selena Simmons-Duffin reports on health policy for NPR.
Rob Stein is a correspondent and senior editor on NPR's science desk.
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